| T O P I C R E V I E W |
| howhurley |
Posted - Oct 22 2009 : 12:14:24 PM
I need to do something, that on it's face, looks elementary, but I thought I'd drop it by you folks and let you shoot holes in it...
I have 250 VDC. I need to operate a single phase cap start 2 hp motor at 230 Vac. A square wave will not do, the 3rd and 5th harmonics are going to smoke things and waste too much energy.
I think a modified sine wave inverter, volt to volt will work. But do I make it microcontroller or 555 controlled? Or something else?
Or do I simply do the PWM thing with a microprocessor?
Any ideas?
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| 4 L A T E S T R E P L I E S (Newest First) |
| howhurley |
Posted - Nov 03 2009 : 3:12:47 PM
Alright. I am going to do it this way: I am going to use an inductor/switch arrangement to boost the voltage to about 375 Volts, then use a microcontroller controlled pwm system to give me a sinusoidal waveform at 230 vac, 10 amps. Is there a good site with inductor calculators or equations available?
Thanks in advance for your expertise. |
| superchad |
Posted - Oct 31 2009 : 5:21:33 PM
230V is RMS, RMS means it does the same thing as DC of the same voltage. except its AC. |
| howhurley |
Posted - Oct 22 2009 : 1:38:41 PM
Of course you are right. d'oh! Of course I will have transform or switch it. I feel stupid. But it won't be the last time.
Now, understanding my simple analog circuits better, (geesh) I still need to generate enough 230 vac power to handle 2 hp. I've read that they seem to all start at 12 VDC, and I want to start at 250 VDC.
Any suggestions how you would do it? I am simply driving a 2 hp cap start motor (actually an A.O. Smith model V1204B) an evaporative cooling motor. I plan to intermittently load it fairly high...I expect to source 2.2 KW for moments at a time. (approx 3 hp) and I am actively cooling the beast, as well as the circuit.
And I have 250 VDC available. Lead-acid Battery power, lots of amps--a WHOLE lot of amps.
Thanks for your knocking me in the right direction. |
| audioguru |
Posted - Oct 22 2009 : 12:54:58 PM
A 230V sine-wave has peak voltages of 325V and is 650V peak-to-peak.
Therefore your 250VDC is a voltage that is way too small. |
